The major objective of this study is to investigate the significance of early mastery motivation for later motivational and intellectual development. This is a follow-up investigation of children on whom measures of mastery motivation were obtained at one year of age. We are interested in determining whether mastery behaviors at one year are predictive of conceptually similar behaviors in the early preschool years, 3 1/2 years. We are also investigating the relations between mastery behaviors at one year and cognitive development at 3 1/2. In addition, we are interested in the role of early experiences in the development of motivation to master and to have an effective impact on the environment.